In the paper "A surface based approach to quantify local gyrification" on TMI. There is a discussion the relation between lGI and curvature-based method. I noticed the following discussion:
"In the current study, all the GI measurements were computed on cortical surfaces based on images in their native space. Independently of intersubject registration, the absence spatial normalization ensures that the observed differences are due to a real decrease in cortical area (related to diminished frequency and depth of sulci) rather than to an effect of scaling."

Given the above discussion, I wonder whether I should follow the freesurfer processing pipeline in generating the pial surface? If not, how should I manage to obtain the pial surface? since I noticed that in the freesurfer pipeline there is a step called Talairach Transformation.

What is the effect of Talairach Transformation on lGI
What is the effect of intersubject registration on lGI?

When I use lGI to measure cortical folding, whether I should follow the freesurfer pipeline or not since there is intersubject registration in the pipeline?
By the way, in your paper, the radius is 20 or 25, what is the exact default value of the radius in freesurfer?

Thanks a lot!

Best regards,

Yuanchao